In one aspect this invention relates to the transportation of water-in-oil emulsion explosives. In another aspect, this invention relates to an improved method of pumping water-in-oil emulsion explosives where the flow is stopped at least once. In still another aspect this invention relates to placement of water-in-oil emulsion explosives.
Water-in-oil emulsion explosives were first disclosed by Bluhm in U.S. Pat. No. 3,447,978. Emulsion explosives normally comprise at least one inorganic oxidizer salt, a carbonaceous fuel, water, oil and an emulsifier. Various other materials, including sensitizing agents and additional fuels, can be employed in a variety of formulations.
The explosives industry has for many years been concerned with the transportation and placement of liquid emulsion type explosives. For example, it is often desirable to pump the emulsion through a hose or pipe into a borehole. Use of emulsion type explosives can be very advantageous. Such explosives are low in cost, high in explosive power and water resistant, making them excellent for general use, especially where underground water is present. Another advantageous property of water-in-oil emulsion explosives is their high viscosity making them resistant to gravity flow. Thus, these emulsions can be used and will stay in position in boreholes that are either horizontal or vertical in inclination. However, emulsion explosives under certain conditions are difficult to pump. Naturally, it would be expected that a fluid of high viscosity, resistant to gravity flow, would have poor pumpability. To facilitate pumping of these emulsions, a pumping method was devised in which water, introduced by a spray ring in an annular stream around the emulsion, flows in the same direction as the emulsion. This method greatly reduces flow resistance of the emulsion and thereby results in reduced pressure requirements. However, often times the pumping operation cannot be stopped or interrupted without the ccurrence of plugging. For example, if the flow is interrupted and the emulsion is allowed to stand in the hose or conduit for more than about 15-20 minutes, the emulsion will swell and plug the delivery hose. Thus, under these conditions, the emulsion often becomes immovable at normal pumping pressures. In the past, it was necessary for the delivery hoses to be flushed out when the pumping operation was stopped overnight, for example. The swelling resulting from contact of the emulsion with the water lubricating film may adversely affect and desensitize the explosive. Accordingly, to fully benefit from the advantages of these explosives, a method was required to overcome the difficulties in transporting and pumping which are presented by the inherent physical properties of these emulsions.